Curious minds want to know ... why no SSB?


Gary DeBock
 

Hi Neil, Kevin and Others,
 
Kevin's detailed explanation concerning the unsuitability of SSB in "consumer-grade" Ultralight radios is quite profound, and reflects the original thinking of John Bryant in setting up the ULR group classification system in early 2008. John solicited ideas from the leaders of the movement at that time (including Kevin, who by the way is the originator of the "Ultralight Radio" moniker), and we all agreed that SSB capability would create an unfair advantage in chasing DX on pocket radios (although at that time, nothing like the G6 existed).
 
DSP capability was discussed by the Definitions Committee (plus John and me) when the first PL-300WT models came out, and we reached a quick consensus that this was a positive change for ULR's, and something that would not create an unfair advantage. The fact that many barefoot ULR DXers continue to prefer traditional models like the SRF-T615 and the E100 confirms that thinking. We had a DSP-related discussion about the multiple filters (which were not originally allowed), and decided to allow them. 
 
As for large external antennas, Neil, the "barefoot" award class rules these out, and would be the perfect competitive forum for those ULR-DXers not enthused with tinkering, monster loops, and similar fanaticism. The "unlimited" ULR award class was essentially set up by two incurable antenna fanatics-- John B. and me. We took great pleasure in trying to outdo each other, and really didn't care how big the antennas became (as long as we were rolling in the TP's at Grayland). Seriously, though, the ULR "Unlimited Class" has really been a boon for antenna experimentation of all types, and if you assess the current AM-DXing community for centers of technical enthusiasm and innovation, you will find that our booming ULR group is right at the top of the list. The combination of relatively cheap receivers and supremely innovative DXers has created this unique situation, a definite tribute to John, Kevin and the other founding fathers.
 
73, Gary DeBock (in Puyallup, WA)  
 
 

In a message dated 8/10/2010 10:53:18 A.M. Pacific Daylight Time, satya@... writes:
 

Hi Neil:

Thanks for your question! I'll put in my two cents.

In general, one of the attractions of Ultralights is that one can take a small consumer-grade, AM-only receiver (as opposed to one built with a DX hobbyist in mind) and still pull in an incredible amount of DX. With the limitation of AM-only, additional skill and luck is required, which is part of the fun and challenge. With SSB or synch, one has the ability to inject/augment the carrier (which enhances the ability to hear a weak or fading station), and more importantly to select an individual sideband, which is a tremendous advantage in tough DX situations. SSB also allows the detection of split-frequency heterodynes, another big advantage when listening for trans-oceanic signals. If one did not want this artificial handicap, then one would use a communications receiver, but for me part of the fun and challenge is to see what can be received using minimal equipment, analogous to crystal set builders who voluntarily place even bigger obstacles in front of themselves. The U LR definitions were crafted with this general principle in mind.

Some receivers now have DSP filtering, but are still exclusively AM receivers without the ability to isolate an individual sideband. As with all AM radios, they can favor one sideband to some degree, but it falls well short of what a synch or SSB-equipped receiver can do. For example, synch and SSB on my Sony 7600GR, even with its ho-hum filtering, make it a better DX rig IMHO than the Tecsun PL-380. Truth be told, the DSP filters on the newer radios don't have particularly good skirt selectivity, compared to even cheap filters found in analog sets, much less the DSP filters on a Perseus SDR: as such, the consumer-grade DSP filtering is something of a trade-off. Also, since DSP is the apparent wave of the future for even cheap consumer-grade receivers, disqualifying DSP sets would eventually rule out buying any new Ultralights(!).

If a small radio had an RF gain control or a pre-amp, being able to boost or cut the RF signal wouldn't, in my experience, provide the same sort of advantage as SSB or synch, and would not be a disqualifier. I am not aware of these controls being in a small, under-$100 set - my guess is that it would cost too much to implement - so it may not ever be an issue. As you say, large external antennas do indeed offer a big advantage, which is why we differentiate between "barefoot" class and "unlimited" class for reception records and contests. Putting new filters and ferrites into off-the-shelf receivers also propels one into the unlimited class. Even with these augmentations, as monstrous as they may be at times, one still has the limitation of processing the signal on a cheap little AM-only receiver.

For me, who like others had lost a degree of enthusiasm for DXing with a communications receiver, Ultralight DXing offered (and continues to offer) a much-appreciated shot in the DX arm for interest and enthusiasm.

Thanks - Kevin S
Bainbridge Island, WA

--- In ultralightdx@..., "neilkj6fba" wrote:
>
> The definition of "Ultralight" radios seemingly excludes radios with SSB
> or sync capabilities since they would have an unfair advantage.
> However, radios with DSP are readily accepted. Does not a DSP radio
> have an advantage of over radios? How about small sized radios with RF
> gain controls or pre-amps? What makes synchronous detection so
> disqualifying?
>
> Does not a LARGE external antenna give an advantage over a "barefoot"
> radio? Is a radio using a 6 foot square directional loop still
> "consumer grade?" Sure doesn't fit in my pocket!
>
> I can certainly understand the goal of keep low cost as a factor in
> ranking a radio as ultralight and also the importance of size. But
> aren't both of these factors stretched substantially when large antennas
> are used to create "records of achievement" or internal modifications
> far beyond the ability of consumers?
>
> I realize that there are criteria for the awards program that divide
> into Barefoot and Unlimited.
>


neilkj6fba <neil.bell@...>
 

The definition of "Ultralight" radios seemingly excludes radios with SSB
or sync capabilities since they would have an unfair advantage.
However, radios with DSP are readily accepted. Does not a DSP radio
have an advantage of over radios? How about small sized radios with RF
gain controls or pre-amps? What makes synchronous detection so
disqualifying?

Does not a LARGE external antenna give an advantage over a "barefoot"
radio? Is a radio using a 6 foot square directional loop still
"consumer grade?" Sure doesn't fit in my pocket!

I can certainly understand the goal of keep low cost as a factor in
ranking a radio as ultralight and also the importance of size. But
aren't both of these factors stretched substantially when large antennas
are used to create "records of achievement" or internal modifications
far beyond the ability of consumers?

I realize that there are criteria for the awards program that divide
into Barefoot and Unlimited.


dmccorm@...
 

On that subject yet, OT. I just read that the G5 is being put on clearance at RadioShack's that have them. Just FYI. It's a great rig in the DE/KA 110x series of radios IMHO.

---- neilkj6fba <neil.bell@...> wrote:

The definition of "Ultralight" radios seemingly excludes radios with SSB
or sync capabilities since they would have an unfair advantage.
However, radios with DSP are readily accepted. Does not a DSP radio
have an advantage of over radios? How about small sized radios with RF
gain controls or pre-amps? What makes synchronous detection so
disqualifying?

Does not a LARGE external antenna give an advantage over a "barefoot"
radio? Is a radio using a 6 foot square directional loop still
"consumer grade?" Sure doesn't fit in my pocket!

I can certainly understand the goal of keep low cost as a factor in
ranking a radio as ultralight and also the importance of size. But
aren't both of these factors stretched substantially when large antennas
are used to create "records of achievement" or internal modifications
far beyond the ability of consumers?

I realize that there are criteria for the awards program that divide
into Barefoot and Unlimited.


Mike Mayer <mwmayer@...>
 

That may be old information. I don’t see the G5 on their web site. Maybe they already sold them all? I suppose individual stores may still have stock.

 

==========================================================
Mike Mayer
mwmayer@...


From: ultralightdx@... [mailto:ultralightdx@...] On Behalf Of dmccorm@...
Sent: Tuesday, August 10, 2010 12:24 PM
To: ultralightdx@...
Subject: Re: [ultralightdx] Curious minds want to know ... why no SSB?

 

 

On that subject yet, OT. I just read that the G5 is being put on clearance at RadioShack's that have them. Just FYI. It's a great rig in the DE/KA 110x series of radios IMHO.

---- neilkj6fba <neil.bell@...> wrote:
> The definition of "Ultralight" radios seemingly excludes radios with SSB
> or sync capabilities since they would have an unfair advantage.
> However, radios with DSP are readily accepted. Does not a DSP radio
> have an advantage of over radios? How about small sized radios with RF
> gain controls or pre-amps? What makes synchronous detection so
> disqualifying?
>
> Does not a LARGE external antenna give an advantage over a "barefoot"
> radio? Is a radio using a 6 foot square directional loop still
> "consumer grade?" Sure doesn't fit in my pocket!
>
> I can certainly understand the goal of keep low cost as a factor in
> ranking a radio as ultralight and also the importance of size. But
> aren't both of these factors stretched substantially when large antennas
> are used to create "records of achievement" or internal modifications
> far beyond the ability of consumers?
>
> I realize that there are criteria for the awards program that divide
> into Barefoot and Unlimited.
>
>


dhsatyadhana <satya@...>
 

Hi Neil:

Thanks for your question! I'll put in my two cents.

In general, one of the attractions of Ultralights is that one can take a small consumer-grade, AM-only receiver (as opposed to one built with a DX hobbyist in mind) and still pull in an incredible amount of DX. With the limitation of AM-only, additional skill and luck is required, which is part of the fun and challenge. With SSB or synch, one has the ability to inject/augment the carrier (which enhances the ability to hear a weak or fading station), and more importantly to select an individual sideband, which is a tremendous advantage in tough DX situations. SSB also allows the detection of split-frequency heterodynes, another big advantage when listening for trans-oceanic signals. If one did not want this artificial handicap, then one would use a communications receiver, but for me part of the fun and challenge is to see what can be received using minimal equipment, analogous to crystal set builders who voluntarily place even bigger obstacles in front of themselves. The ULR definitions were crafted with this general principle in mind.

Some receivers now have DSP filtering, but are still exclusively AM receivers without the ability to isolate an individual sideband. As with all AM radios, they can favor one sideband to some degree, but it falls well short of what a synch or SSB-equipped receiver can do. For example, synch and SSB on my Sony 7600GR, even with its ho-hum filtering, make it a better DX rig IMHO than the Tecsun PL-380. Truth be told, the DSP filters on the newer radios don't have particularly good skirt selectivity, compared to even cheap filters found in analog sets, much less the DSP filters on a Perseus SDR: as such, the consumer-grade DSP filtering is something of a trade-off. Also, since DSP is the apparent wave of the future for even cheap consumer-grade receivers, disqualifying DSP sets would eventually rule out buying any new Ultralights(!).

If a small radio had an RF gain control or a pre-amp, being able to boost or cut the RF signal wouldn't, in my experience, provide the same sort of advantage as SSB or synch, and would not be a disqualifier. I am not aware of these controls being in a small, under-$100 set - my guess is that it would cost too much to implement - so it may not ever be an issue. As you say, large external antennas do indeed offer a big advantage, which is why we differentiate between "barefoot" class and "unlimited" class for reception records and contests. Putting new filters and ferrites into off-the-shelf receivers also propels one into the unlimited class. Even with these augmentations, as monstrous as they may be at times, one still has the limitation of processing the signal on a cheap little AM-only receiver.

For me, who like others had lost a degree of enthusiasm for DXing with a communications receiver, Ultralight DXing offered (and continues to offer) a much-appreciated shot in the DX arm for interest and enthusiasm.

Thanks - Kevin S
Bainbridge Island, WA

--- In ultralightdx@..., "neilkj6fba" <neil.bell@...> wrote:

The definition of "Ultralight" radios seemingly excludes radios with SSB
or sync capabilities since they would have an unfair advantage.
However, radios with DSP are readily accepted. Does not a DSP radio
have an advantage of over radios? How about small sized radios with RF
gain controls or pre-amps? What makes synchronous detection so
disqualifying?

Does not a LARGE external antenna give an advantage over a "barefoot"
radio? Is a radio using a 6 foot square directional loop still
"consumer grade?" Sure doesn't fit in my pocket!

I can certainly understand the goal of keep low cost as a factor in
ranking a radio as ultralight and also the importance of size. But
aren't both of these factors stretched substantially when large antennas
are used to create "records of achievement" or internal modifications
far beyond the ability of consumers?

I realize that there are criteria for the awards program that divide
into Barefoot and Unlimited.


ferrite61 <dxrx@...>
 

Actually, RF-Bosters are in Ultralights... just not intended for the AM-BCB. Both the Eton E100 and Tecsun PL-200 have them, and I presume the new PL-210 will also have it. These work on FM and SW freqiencies.

Paul S. in CT

--- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote:

If a small radio had an RF gain control or a pre-amp, being able to boost or cut the RF signal wouldn't, in my experience, provide the same sort of advantage as SSB or synch, and would not be a disqualifier. I am not aware of these controls being in a small, under-$100 set - my guess is that it would cost too much to implement - so it may not ever be an issue. As you say, large external antennas do indeed offer a big advantage, which is why we differentiate between "barefoot" class and "unlimited" class for reception records and contests. Putting new filters and ferrites into off-the-shelf receivers also propels one into the unlimited class. Even with these augmentations, as monstrous as they may be at times, one still has the limitation of processing the signal on a cheap little AM-only receiver.

Thanks - Kevin S
Bainbridge Island, WA


sdwillingham
 

--- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote:
Truth be told, the DSP filters on the newer radios don't have particularly
good skirt selectivity, compared to even cheap filters found in analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-


Kevin S <satya@...>
 

Hi Scott:

I did the comparisons as part of the G8/PL-300WT review I did a few months
ago. Look in "Files > 3 Radios, Reviews, Manuals > Radio Reviews" for the
"Grundig G8 Review.pdf" here on the Yahoo site. The G8's response was
using the LCD display, while the other filter info was either from Murata
datasheets or Steve Ratzlaff's careful measurements of single and cascaded
filters. Note that skirt selectivity figures for the DSP filtering is
something of an estimate.

As you will see, the DSP skirts are pretty good, based on my findings, but
not up to the Murata filters. However, I'm glad you made me go back and
look at this info! In looking at the graph (page 3 of the review), I may
have to retract my statement below - the filters that are found on typical
analog portables may in fact have noticeably poorer skirt selectivity.
For instance, the Eton e100's P55I filter, about as good as it gets on
analog Ultralights, is clearly worse than the 3 khz DSP filter on the G8,
even when there are two P55I's cascaded.

I say I "may" have to retract my statement, since to some extent this is
comparing apples and oranges. For instance, the P55I is obviously
designed to be a wider filter, given the -6 dB intercept figures. Perhaps
a better comparison would be the 4 or 6 khz DSP filter on the Tecsun
PL-380, which would presumably have a similar -6 dB intercept, and then we
could see what the deal is at -60 dB (I may have a project tonight!). Who
knows - the P55I may come out on top in that case.

I would also be curious to see the response curves for the filters
installed in more sophisticated portables (Sony 2010's stock narrow
filter, the Tecsun PL-450 narrow filter, etc.) to see how the DSP skirts
compare.

Thanks - Kevin


--- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote:
Truth be told, the DSP filters on the newer radios don't have
particularly
good skirt selectivity, compared to even cheap filters found in analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-


pianoplayer88key
 

I'm finding the AM skirt selectivity is atrocious on my PL-380. The FM, however, is quite good. Recently (probably a few weeks ago now) I was near the tower site of a combined AM (KOGO-600, IBOC, 5kW DA) and FM (KLNV-106.5, 50kW). The RSSI,SNR readings on FM around the 106.5 were approx 63,43 on 106.5kHz, about 10dBu or so +/- 0.2MHz, and zeros +/-0.4 MHz.
I'm on my way home from near the KCBQ-1170 (50kW) / KECR-910 (5kW) site, where I was comparing the PL-380, my Panasonic RQ-SW20, and my Zenith Royal 705 portable radio.
Basically, the PL-380 got OWNED by the other two radios. Other than traces of a few other stations, KECR and KCBQ were the ONLY AM stations received with any form of a decent signal, with KCBQ often overloading the audio amplifier. When I combined the Select-A-Tenna, power pole and PL-380, it completely overloaded. The 18th harmonic, 21060kHz, was indicating 63dBu, and in the FM band, it was indicating 13-14dBu at 64MHz and 1-2dBu at 108MHz. On the fundamental frequency with that combination, the audio amplifier completely shuts down, and in fact one time actually read 00,00 (dBu RSSI, dB SNR) on 1170kHz.
As I mentioned, I compared the above 3 mentioned radios, although I did it about 1/8 to 1/4 mile down the street where the radios wouldn't be likely to overload. To summarize, the PL-380 struggled with all but the strongest stations (910 and 1170, plus a few at the low end of the band.) Several stations were clearly audible on the RQ-SW20 which had no trace on the PL-380, and others had some crosstalk from 1170. These included 1700, 1630, 1470, 1360, 860, 800, 760, 690, 620, 600, plus a few others. In addition, the Zenith was able to hear stations on 1130, 1090 and 1040 that the Panasonic and Tecsun struggled with, although all 3 radios were virtually hopeless for 1210 and 1240.
I didn't even bother trying for KERN-1180 from Wasco-Greenacres, CA. With a nearby strong signal like what I described (I estimate about 40,000 to 75,000 mv/m before amplification where I was near the tower site, based on calculations using FCC data and Google Maps/Earth, and the SAT+powerpole appears to amplify to a level where I'd have to be about 100 times closer, based on other calculations I've done), and considering that location is about twice as far as radio-locator's predicted 0.15mV/m comtour, would even a high-end communications receiver struggle trying to hear 1180 next to 1170?
I also plan to take my radios to a site some distance out of town where there isn't much in the way of nearby strong signals, and do some sensitivity comparisons, although the timing hasn't been planned yet.
Kevin, would I be correct to assume you did NOT do the reviews while you were right outside the fence surrounding the site of a 50kW AM blowtorch? ;)
Scott, what do I need to do with my PL-380 to get its AM section skirt selectivity to match that of the FM, relative to the -3dB or -6dB bandwidth?

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hi Scott:

I did the comparisons as part of the G8/PL-300WT review I did a few months
ago. Look in "Files > 3 Radios, Reviews, Manuals > Radio Reviews" for the
"Grundig G8 Review.pdf" here on the Yahoo site. The G8's response was
using the LCD display, while the other filter info was either from Murata
datasheets or Steve Ratzlaff's careful measurements of single and cascaded
filters. Note that skirt selectivity figures for the DSP filtering is
something of an estimate.

As you will see, the DSP skirts are pretty good, based on my findings, but
not up to the Murata filters. However, I'm glad you made me go back and
look at this info! In looking at the graph (page 3 of the review), I may
have to retract my statement below - the filters that are found on typical
analog portables may in fact have noticeably poorer skirt selectivity.
For instance, the Eton e100's P55I filter, about as good as it gets on
analog Ultralights, is clearly worse than the 3 khz DSP filter on the G8,
even when there are two P55I's cascaded.

I say I "may" have to retract my statement, since to some extent this is
comparing apples and oranges. For instance, the P55I is obviously
designed to be a wider filter, given the -6 dB intercept figures. Perhaps
a better comparison would be the 4 or 6 khz DSP filter on the Tecsun
PL-380, which would presumably have a similar -6 dB intercept, and then we
could see what the deal is at -60 dB (I may have a project tonight!). Who
knows - the P55I may come out on top in that case.

I would also be curious to see the response curves for the filters
installed in more sophisticated portables (Sony 2010's stock narrow
filter, the Tecsun PL-450 narrow filter, etc.) to see how the DSP skirts
compare.

Thanks - Kevin



--- In ultralightdx@..., "dhsatyadhana" <satya@> wrote:
Truth be told, the DSP filters on the newer radios don't have
particularly
good skirt selectivity, compared to even cheap filters found in analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-


dhsatyadhana <satya@...>
 

Hey Stephen:

I think that is another symptom of the overloads that occur in your location. With all that RF energy flying around, it's not hard to imagine that the front end gets desensitized. It happens to me here in Seattle on some days.

Kevin

--- In ultralightdx@..., "Stephen" <pianoplayer88key@...> wrote:

I'm finding the AM skirt selectivity is atrocious on my PL-380. The FM, however, is quite good. Recently (probably a few weeks ago now) I was near the tower site of a combined AM (KOGO-600, IBOC, 5kW DA) and FM (KLNV-106.5, 50kW). The RSSI,SNR readings on FM around the 106.5 were approx 63,43 on 106.5kHz, about 10dBu or so +/- 0.2MHz, and zeros +/-0.4 MHz.
I'm on my way home from near the KCBQ-1170 (50kW) / KECR-910 (5kW) site, where I was comparing the PL-380, my Panasonic RQ-SW20, and my Zenith Royal 705 portable radio.
Basically, the PL-380 got OWNED by the other two radios. Other than traces of a few other stations, KECR and KCBQ were the ONLY AM stations received with any form of a decent signal, with KCBQ often overloading the audio amplifier. When I combined the Select-A-Tenna, power pole and PL-380, it completely overloaded. The 18th harmonic, 21060kHz, was indicating 63dBu, and in the FM band, it was indicating 13-14dBu at 64MHz and 1-2dBu at 108MHz. On the fundamental frequency with that combination, the audio amplifier completely shuts down, and in fact one time actually read 00,00 (dBu RSSI, dB SNR) on 1170kHz.
As I mentioned, I compared the above 3 mentioned radios, although I did it about 1/8 to 1/4 mile down the street where the radios wouldn't be likely to overload. To summarize, the PL-380 struggled with all but the strongest stations (910 and 1170, plus a few at the low end of the band.) Several stations were clearly audible on the RQ-SW20 which had no trace on the PL-380, and others had some crosstalk from 1170. These included 1700, 1630, 1470, 1360, 860, 800, 760, 690, 620, 600, plus a few others. In addition, the Zenith was able to hear stations on 1130, 1090 and 1040 that the Panasonic and Tecsun struggled with, although all 3 radios were virtually hopeless for 1210 and 1240.
I didn't even bother trying for KERN-1180 from Wasco-Greenacres, CA. With a nearby strong signal like what I described (I estimate about 40,000 to 75,000 mv/m before amplification where I was near the tower site, based on calculations using FCC data and Google Maps/Earth, and the SAT+powerpole appears to amplify to a level where I'd have to be about 100 times closer, based on other calculations I've done), and considering that location is about twice as far as radio-locator's predicted 0.15mV/m comtour, would even a high-end communications receiver struggle trying to hear 1180 next to 1170?
I also plan to take my radios to a site some distance out of town where there isn't much in the way of nearby strong signals, and do some sensitivity comparisons, although the timing hasn't been planned yet.
Kevin, would I be correct to assume you did NOT do the reviews while you were right outside the fence surrounding the site of a 50kW AM blowtorch? ;)
Scott, what do I need to do with my PL-380 to get its AM section skirt selectivity to match that of the FM, relative to the -3dB or -6dB bandwidth?


--- In ultralightdx@..., "Kevin S" <satya@> wrote:

Hi Scott:

I did the comparisons as part of the G8/PL-300WT review I did a few months
ago. Look in "Files > 3 Radios, Reviews, Manuals > Radio Reviews" for the
"Grundig G8 Review.pdf" here on the Yahoo site. The G8's response was
using the LCD display, while the other filter info was either from Murata
datasheets or Steve Ratzlaff's careful measurements of single and cascaded
filters. Note that skirt selectivity figures for the DSP filtering is
something of an estimate.

As you will see, the DSP skirts are pretty good, based on my findings, but
not up to the Murata filters. However, I'm glad you made me go back and
look at this info! In looking at the graph (page 3 of the review), I may
have to retract my statement below - the filters that are found on typical
analog portables may in fact have noticeably poorer skirt selectivity.
For instance, the Eton e100's P55I filter, about as good as it gets on
analog Ultralights, is clearly worse than the 3 khz DSP filter on the G8,
even when there are two P55I's cascaded.

I say I "may" have to retract my statement, since to some extent this is
comparing apples and oranges. For instance, the P55I is obviously
designed to be a wider filter, given the -6 dB intercept figures. Perhaps
a better comparison would be the 4 or 6 khz DSP filter on the Tecsun
PL-380, which would presumably have a similar -6 dB intercept, and then we
could see what the deal is at -60 dB (I may have a project tonight!). Who
knows - the P55I may come out on top in that case.

I would also be curious to see the response curves for the filters
installed in more sophisticated portables (Sony 2010's stock narrow
filter, the Tecsun PL-450 narrow filter, etc.) to see how the DSP skirts
compare.

Thanks - Kevin



--- In ultralightdx@..., "dhsatyadhana" <satya@> wrote:
Truth be told, the DSP filters on the newer radios don't have
particularly
good skirt selectivity, compared to even cheap filters found in analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-


pianoplayer88key
 

I've noticed that desensitization here, too, although the worst it gets at my home location is such that the RSSI at +/-15kHz from my local strongest blowtorches is 45,00 around 1170 daytime, and 43,00 around 760 nighttime. If I'm close to strong stations, it's 50,00 over quite a wide portion of the band, and when I did my SAT + powerpole experiment right outside the site of the 50kW KCBQ earlier today, where the audio section completely shut down, it was indicating 63,00 across the band, except when it briefly showed 00,00 on 1170.
On the other hand, in areas or bands with less signal, the RSSI bottoms out at 15dBu, which it typically is at outside the AM band (and about 15-17 at 520 and 22 at 1710 in the daytime). In fact, under the right conditions, I was getting 15,25 readings on 2340kHz, the. 2nd harmonic of 1170, my strongest blowtorch, with a signal that actually sounded quite clean, with a little noise.

--- In ultralightdx@..., "dhsatyadhana" <satya@...> wrote:

Hey Stephen:

I think that is another symptom of the overloads that occur in your location. With all that RF energy flying around, it's not hard to imagine that the front end gets desensitized. It happens to me here in Seattle on some days.

Kevin

--- In ultralightdx@..., "Stephen" <pianoplayer88key@> wrote:

I'm finding the AM skirt selectivity is atrocious on my PL-380. The FM, however, is quite good. Recently (probably a few weeks ago now) I was near the tower site of a combined AM (KOGO-600, IBOC, 5kW DA) and FM (KLNV-106.5, 50kW). The RSSI,SNR readings on FM around the 106.5 were approx 63,43 on 106.5kHz, about 10dBu or so +/- 0.2MHz, and zeros +/-0.4 MHz.
I'm on my way home from near the KCBQ-1170 (50kW) / KECR-910 (5kW) site, where I was comparing the PL-380, my Panasonic RQ-SW20, and my Zenith Royal 705 portable radio.
Basically, the PL-380 got OWNED by the other two radios. Other than traces of a few other stations, KECR and KCBQ were the ONLY AM stations received with any form of a decent signal, with KCBQ often overloading the audio amplifier. When I combined the Select-A-Tenna, power pole and PL-380, it completely overloaded. The 18th harmonic, 21060kHz, was indicating 63dBu, and in the FM band, it was indicating 13-14dBu at 64MHz and 1-2dBu at 108MHz. On the fundamental frequency with that combination, the audio amplifier completely shuts down, and in fact one time actually read 00,00 (dBu RSSI, dB SNR) on 1170kHz.
As I mentioned, I compared the above 3 mentioned radios, although I did it about 1/8 to 1/4 mile down the street where the radios wouldn't be likely to overload. To summarize, the PL-380 struggled with all but the strongest stations (910 and 1170, plus a few at the low end of the band.) Several stations were clearly audible on the RQ-SW20 which had no trace on the PL-380, and others had some crosstalk from 1170. These included 1700, 1630, 1470, 1360, 860, 800, 760, 690, 620, 600, plus a few others. In addition, the Zenith was able to hear stations on 1130, 1090 and 1040 that the Panasonic and Tecsun struggled with, although all 3 radios were virtually hopeless for 1210 and 1240.
I didn't even bother trying for KERN-1180 from Wasco-Greenacres, CA. With a nearby strong signal like what I described (I estimate about 40,000 to 75,000 mv/m before amplification where I was near the tower site, based on calculations using FCC data and Google Maps/Earth, and the SAT+powerpole appears to amplify to a level where I'd have to be about 100 times closer, based on other calculations I've done), and considering that location is about twice as far as radio-locator's predicted 0.15mV/m comtour, would even a high-end communications receiver struggle trying to hear 1180 next to 1170?
I also plan to take my radios to a site some distance out of town where there isn't much in the way of nearby strong signals, and do some sensitivity comparisons, although the timing hasn't been planned yet.
Kevin, would I be correct to assume you did NOT do the reviews while you were right outside the fence surrounding the site of a 50kW AM blowtorch? ;)
Scott, what do I need to do with my PL-380 to get its AM section skirt selectivity to match that of the FM, relative to the -3dB or -6dB bandwidth?


--- In ultralightdx@..., "Kevin S" <satya@> wrote:

Hi Scott:

I did the comparisons as part of the G8/PL-300WT review I did a few months
ago. Look in "Files > 3 Radios, Reviews, Manuals > Radio Reviews" for the
"Grundig G8 Review.pdf" here on the Yahoo site. The G8's response was
using the LCD display, while the other filter info was either from Murata
datasheets or Steve Ratzlaff's careful measurements of single and cascaded
filters. Note that skirt selectivity figures for the DSP filtering is
something of an estimate.

As you will see, the DSP skirts are pretty good, based on my findings, but
not up to the Murata filters. However, I'm glad you made me go back and
look at this info! In looking at the graph (page 3 of the review), I may
have to retract my statement below - the filters that are found on typical
analog portables may in fact have noticeably poorer skirt selectivity.
For instance, the Eton e100's P55I filter, about as good as it gets on
analog Ultralights, is clearly worse than the 3 khz DSP filter on the G8,
even when there are two P55I's cascaded.

I say I "may" have to retract my statement, since to some extent this is
comparing apples and oranges. For instance, the P55I is obviously
designed to be a wider filter, given the -6 dB intercept figures. Perhaps
a better comparison would be the 4 or 6 khz DSP filter on the Tecsun
PL-380, which would presumably have a similar -6 dB intercept, and then we
could see what the deal is at -60 dB (I may have a project tonight!). Who
knows - the P55I may come out on top in that case.

I would also be curious to see the response curves for the filters
installed in more sophisticated portables (Sony 2010's stock narrow
filter, the Tecsun PL-450 narrow filter, etc.) to see how the DSP skirts
compare.

Thanks - Kevin



--- In ultralightdx@..., "dhsatyadhana" <satya@> wrote:
Truth be told, the DSP filters on the newer radios don't have
particularly
good skirt selectivity, compared to even cheap filters found in analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-


Rick Robinson <w4dst@...>
 

On 8/10/2010 10:35 PM, Stephen wrote:
I'm finding the AM skirt selectivity is atrocious on my PL-380.
What you are measuring with your transmitter tower experiments, as has been discussed on the list before, is not IF selectivilty, but front end selectivity and overload. This is an entirely different matter than IF selectivity. Although I don't have schematics of your 2 non-DSP radios, I am almost certain that they have no IF filters. What IF selectivity they do have is from the Q of the IF transformers and from the alignment of the transformers to the IF frequency, usually 455kHz. If you were to compare IF selectivity of these 3 radios, my money is on the PL-380 blowing the other 2 away. Please understand, the DSP filtering is in the IF of the radio, your overloading is in the RF section of the radio. These are 2 entirely different parts of the radio and accurate IF selectivity measurements are done on a bench with quality test equipment or software.
I also plan to take my radios to a site some distance out of town where there isn't much in the way of nearby strong signals, and do some sensitivity comparisons, although the timing hasn't been planned yet.
This is a much better test of radio performance that being very close to a transmitting tower or coupling your SAT into a power pole ground cable. Please share your findings with the list when you do go out of the urban area you're in. Compare them by only coupling them to the SAT and nothing else.

Scott, what do I need to do with my PL-380 to get its AM section skirt selectivity to match that of the FM, relative to the -3dB or -6dB bandwidth?

The IF selectivity of the FM section is probably in the neighborhood of 100kHz. I doubt you would want that in the AM section.

Rick W4DST


sdwillingham
 

Thanks for the detailed reply, Kevin. Your data plotted
in the G8 review is an excellent comparison. I think the
G8 curve is pretty close to what I'd expect; perhaps a
little off at the last couple points. I think the DSP
filter is actually slightly tighter.

Looking at some proprietary data I have access to, I think
you'll find a favorable comparison of the 4 and 6 kHz
DSP filters to the P55I. The DSP filter shape factors
(ratio of 60 dB point to 6 dB point) actually improve for
the wider bandwidth settings. Also, the DSP filter skirts
smoothly plunge past -70 to -80 dB, with no "flaring out"
of the response.

-Scott-

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hi Scott:

I did the comparisons as part of the G8/PL-300WT review I did a few months
ago. Look in "Files > 3 Radios, Reviews, Manuals > Radio Reviews" for the
"Grundig G8 Review.pdf" here on the Yahoo site. The G8's response was
using the LCD display, while the other filter info was either from Murata
datasheets or Steve Ratzlaff's careful measurements of single and cascaded
filters. Note that skirt selectivity figures for the DSP filtering is
something of an estimate.

As you will see, the DSP skirts are pretty good, based on my findings, but
not up to the Murata filters. However, I'm glad you made me go back and
look at this info! In looking at the graph (page 3 of the review), I may
have to retract my statement below - the filters that are found on typical
analog portables may in fact have noticeably poorer skirt selectivity.
For instance, the Eton e100's P55I filter, about as good as it gets on
analog Ultralights, is clearly worse than the 3 khz DSP filter on the G8,
even when there are two P55I's cascaded.

I say I "may" have to retract my statement, since to some extent this is
comparing apples and oranges. For instance, the P55I is obviously
designed to be a wider filter, given the -6 dB intercept figures. Perhaps
a better comparison would be the 4 or 6 khz DSP filter on the Tecsun
PL-380, which would presumably have a similar -6 dB intercept, and then we
could see what the deal is at -60 dB (I may have a project tonight!). Who
knows - the P55I may come out on top in that case.

I would also be curious to see the response curves for the filters
installed in more sophisticated portables (Sony 2010's stock narrow
filter, the Tecsun PL-450 narrow filter, etc.) to see how the DSP skirts
compare.

Thanks - Kevin



--- In ultralightdx@..., "dhsatyadhana" <satya@> wrote:
Truth be told, the DSP filters on the newer radios don't have
particularly
good skirt selectivity, compared to even cheap filters found in analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-


sdwillingham
 

Stephen,

I think I've said this before, but it bears repeating:

Most radio specifications are defined to be applied
only when the radio is not in an overload condition. In
particular, the IF filter selectivity we are discussing
pertains to a filter that follows several stages of
processing. If those preceding stages are driven to
a nonlinear point, distortion frequencies are generated
in a way that no filter can "undo".

This is not to denigrate the importance of radio performance
at high signal levels. But the specifications for such
operation are different and in fact more complex. In
general, however, a radio with *less* front-end sensitivity
will distort less (under strong signal conditions) and
therefore "own" a radio with more front-end sensitivity.
In the presence of extremely strong signals, you will
improve the radio's performance by attenuating the signals
(or equivalently, using a radio with lower-gain amplifiers).

-Scott-


Kevin S <satya@...>
 

Thanks Scott. I wish I had access to your proprietary data!

One of my limitations was that, being in an urban area, my -60 db readings
were difficult, since I was bumping up against the 20 or so dB RSSI
general noise level across the band. That your info indicates that the
skirts are even tighter is good to know.

By any chance can you give us an idea of what the skirts on the 1 khz
filter setting are like???

Thanks - Kevin


Thanks for the detailed reply, Kevin. Your data plotted
in the G8 review is an excellent comparison. I think the
G8 curve is pretty close to what I'd expect; perhaps a
little off at the last couple points. I think the DSP
filter is actually slightly tighter.

Looking at some proprietary data I have access to, I think
you'll find a favorable comparison of the 4 and 6 kHz
DSP filters to the P55I. The DSP filter shape factors
(ratio of 60 dB point to 6 dB point) actually improve for
the wider bandwidth settings. Also, the DSP filter skirts
smoothly plunge past -70 to -80 dB, with no "flaring out"
of the response.

-Scott-

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hi Scott:

I did the comparisons as part of the G8/PL-300WT review I did a few
months
ago. Look in "Files > 3 Radios, Reviews, Manuals > Radio Reviews" for
the
"Grundig G8 Review.pdf" here on the Yahoo site. The G8's response was
using the LCD display, while the other filter info was either from
Murata
datasheets or Steve Ratzlaff's careful measurements of single and
cascaded
filters. Note that skirt selectivity figures for the DSP filtering is
something of an estimate.

As you will see, the DSP skirts are pretty good, based on my findings,
but
not up to the Murata filters. However, I'm glad you made me go back and
look at this info! In looking at the graph (page 3 of the review), I
may
have to retract my statement below - the filters that are found on
typical
analog portables may in fact have noticeably poorer skirt selectivity.
For instance, the Eton e100's P55I filter, about as good as it gets on
analog Ultralights, is clearly worse than the 3 khz DSP filter on the
G8,
even when there are two P55I's cascaded.

I say I "may" have to retract my statement, since to some extent this is
comparing apples and oranges. For instance, the P55I is obviously
designed to be a wider filter, given the -6 dB intercept figures.
Perhaps
a better comparison would be the 4 or 6 khz DSP filter on the Tecsun
PL-380, which would presumably have a similar -6 dB intercept, and then
we
could see what the deal is at -60 dB (I may have a project tonight!).
Who
knows - the P55I may come out on top in that case.

I would also be curious to see the response curves for the filters
installed in more sophisticated portables (Sony 2010's stock narrow
filter, the Tecsun PL-450 narrow filter, etc.) to see how the DSP skirts
compare.

Thanks - Kevin



--- In ultralightdx@..., "dhsatyadhana" <satya@> wrote:
Truth be told, the DSP filters on the newer radios don't have
particularly
good skirt selectivity, compared to even cheap filters found in
analog
sets, much less the DSP filters on a Perseus SDR: as such, the
consumer-grade DSP filtering is something of a trade-off.
Kevin,

Could you elaborate on this please? In what ways are the DSP filters
in the Tecsun receivers inferior to any analog portable radios? How
did you measure this?

-Scott-